This is a Phase II study of the safety and efficacy of TAK-603/A-165646 in patients with Crohn's disease. The primary efficacy endpoint of this study will be a percentage of patients achieving remission, defined as a CDAI score of 150 or less. Secondary endpoints will include percentage of patients achieving improvement in symptoms, indicated by a reduction in baseline CDAI by at least 50 points, percentage of patients classified as treatment failure, and changes in physicians global assessment of disease activity, patients global assessment of disease activity, laboratory measure of inflammatory activity and qualify of life evaluations.